The instant invention pertains to a multi-layer tamper proof electronic coating. The multi-layer coating is applied to the device chip at the wafer fabrication stage.
The dissection of electronic devices is a major source of information for both commercial competitors as well as foreign governments. The devices may be analyzed by numerous techniques such as x-rays, cross-sectioning, etching and others. Because of the ability to analyze the devices it has become desirable to make the electronic devices resistant to the numerous analytical techniques.
The use of certain fillers to improve the tamper-proof characteristics of electronic coatings is known in the art. For example, U.S. Pat. No. 5,258,334 to Lantz, II, U.S. Pat. No. 5,399,441 to Bearinger et al., U.S. Pat. No. 5,387,480 to Haluska et al., U.S. Pat. No. 5,436,083 to Haluska et al., U.S. Pat. No. 5,436,084 to Haluska et al., U.S. Pat. No. 5,458,912 to Camilletti et al.; U.S. Pat. No. 5,492,958 to Haluska et al. and EP 0615000 all disclose coating compositions comprising a filler and a preceramic silicon containing material, borosilazane or polysilazane. The fillers disclosed in the above patents impart a variety of properties to the coating such as opaqueness, radiopaqueness, or resistance to plasma etching, wet etching or cross-sectioning. In addition to the filled electronic coating there may be other coatings applied to the electronic substrate to provide protection from the environment or make the devices further resistant to the analytical techniques.
The coatings taught in the above patents are not resistant to erosion, delamination and/or separation and thus the coatings could be removed from the device. Thus, it is desirable to produce a multi-layer coating for electronic devices that is resistant to analytical techniques, erosion, delamination and/or separation and optionally the environment.
It is therefore an object of the instant invention to provide a multi-layer tamper-proof electronic coating comprising a first protecting layer, a second sealer layer, an optional third capping layer and an optional fourth overcoat layer.